PLASMONS: A modern form of super particle waves
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The document discusses surface plasmons, which are coherent electron oscillations that exist at the interface between two materials like metal and air. Surface plasmon polaritons are electromagnetic waves that travel along such an interface and involve both charge motion in the metal and electromagnetic waves. They have applications in improving solar cell efficiency through increased light absorption and extraction, as well as medical uses like cancer therapy.
PLASMONS: A modern form of super particle waves
- 1. The Lycurgus Cup, which is kept in London museum, is a 4th- century Roman glass cage cup made of a dichroic glass, which shows a different color. What is the basic reason behind it?
- 3. What is Plasmons? • When the light incidents on the metal surface, under ideal conditions, it emits the waves which have certain density, known as Plasmons. • A Plasmon is a collective oscillation of the conduction electrons.
- 4. Plasmons can be described in the classical picture as an oscillation of free electron density with respect to the fixed positive ions in a metal. To visualize a plasma oscillation, imagine a cube of metal placed in an external electric field pointing to the right. Electrons will move to the left side (uncovering positive ions on the right side) until they cancel the field inside the metal. If the electric field is removed, the electrons move to the right, repelled by each other and attracted to the positive ions left bare on the right side. They oscillate back and forth at the plasma frequency until then energy is lost in some kind of resistance or damping. Plasmons are a quantization of this kind of oscillation.
- 5. Surface Plasmons • Surface Plasmons (SPs) are coherent electron oscillations that exist at the interface between any two materials, e.g. a metal-dielectric interface, such as a metal sheet in air. • SPs have lower energy than bulk (or volume) Plasmons which quantise the longitudinal electron oscillations about positive ion cores within the bulk of an electron gas (or plasma).
- 6. Surface Plasma Polariton The charge motion in a surface Plasmon always creates electromagnetic fields outside (as well as inside) the metal. The total excitation, including both the charge motion and associated electromagnetic field, is surface Plasmon Polariton. They are a type of surface wave, guided along the interface in much the same way that light can be guided by an optical fiber.
- 7. Surface Plasmon polaritons (SPPs), are infrared or visible- frequency electromagnetic waves, which travel along a metal-dielectric or metal-air interface. The term "surface Plasmon Polariton" explains that the wave involves both charge motion in the metal ("surface Plasmon") and electromagnetic waves in the air or dielectric ("Polariton"). • An SPP will propagate along the interface until its energy is lost either to absorption in the metal or scattering into other directions (such as into free space).
- 8. Plasmonics SPPs are shorter in wavelength than the incident light (photons). Hence, SPPs can have tighter spatial confinement and higher local field intensity. • The short-wavelength of it (around 70 nm) enables the use of Nano scale structure, in which light can be guided, split, filtered, and even amplified. • So, the information transfer in Nano scale structures by means of surface Plasmons, is referred to as Plasmonics.
- 9. One more advantage this gives is, by varying Nano particle shape or geometry, the SP resonance frequency can be tuned over a broad spectral range. • Nano scale structure is used because, one way to achieve long propagation lengths is to use very thin films. • In addition to that, Nano particles show strong optical resonances, because of their large free-electron density and ordered arrays of Nano particles can possess even further enhanced field intensities which will aid the Plasmon coupling between two adjacent particles.
- 10. Plasmonic Solar cell: • Total solar energy striking to the earth is 1,20,000 TW. • The price of soar electricity has decreased by a factor of 5 over the last 20 years • But solar electricity is still currently about 5 times the cost of coal generated • 50% of the cost of solar modules is the cost of the silicon wafers (300μm thick). This can be reduced with thin film cells (~2 μm thick). • Improving the efficiency of photovoltaic cells is one of the great challenges for renewable energy science. • In the lab, the best cells can convert almost half the sunlight hitting them into electricity (44 per cent) although for the figure commercial cells is less than half that.
- 11. One way to improve matters is to minimize the amount of light reflected from the cell or transmitted through it, since this energy is clearly lost. The conventional approach is to use an anti-reflection coating. But there’s a problem. • While these coatings are good at preventing reflections, they cannot stop light being transmitted. • In some cases, almost half the light passes straight through.
- 12. Light-trapping in Photovoltaic: Wafer based cells use light trapping based on geometrical optics (feature sizes ~10 μm). Thin film cells require wavelength-scale light trapping. One way to achieve this is through excitation of Surface Plasmons.
- 13. Types of Plasmons: Localized Plasmons Dipole (and multipole) oscillations of electrons Propagating Plasmons (Surface Plasmon Polaritons) Both types of Plasmons can be used to enhance absorption in solar cells.
- 14. Increased Absorption of light in thin films solar cells Light incident on metal particles roughly on the scale of the wavelength of light can excite Surface Plasmons which can then scatter light and couple it into the waveguide modes.
- 15. Extraction of light from light emitting diodes is also enhanced: Most emitted light is trapped in the semiconductor layer by total internal reflection. Surface Plasmons can couple the light out of the semiconductor waveguide before it is re-absorbed potentially increasing the efficiency of the LED.
- 16. How Light-Trapping Surfaces Will Boost Solar Cell Efficiency: • The basic principle behind “Plasmons” is very simple. Plasmons will work as Nano-antenna. • Plasmons will absorb sun-light having specific wavelength. • While focusing on a different approach– Plasmons captures the incoming light and trapping it against the surface. • This prevents both reflection and transmission and so has the potential to significantly increase the efficiency of thin film solar cells. • We have to cover a cell with a regular array of silver Nano- antennas that convert ordinary incoming waves into more exotic ones that propagate through the photovoltaic slab itself.
- 17. Plasmons Hologram: 3D without spectacles!! The Scientists of Ashoka University said that the viewers can have the 3d effect at any angle and they are not required to have any special spectacles for that. • They developed 3d hologram using surface Plasmons. • They used photo resistive material and Nano Au layers to produce a hologram. • With the light incident below the glass sheet, the Plasmons are activated and excited and with the use of interference, diffraction, light intensity recording and suitable illumination and specific colour wavelengths, they produced hologram.
- 18. Cancer Therapy by gold particles • This Plasmon technology will bring revolution in medical field, especially in Cancer treatment. • A scientist of Rice University successfully removed the cancer tumour with the help of Plasmonics. • A silicon particle is placed into 100 nm golden particle and is injected into blood which approaches to the tumour cell. • This Plasmon particle is heated through infrared radiation and destroys the cancer tumour.
- 19. CMOS chip for sharper image Plasmonics can also be used to make super sensitive image sensor which will give sharper pictures. CMOS( Complementary metal oxide semi-conductor) sensor is used in digital cameras. The scientists of Glasgow University, Scotland are researching on that super sensitive sensor which consists of Nano structure layer on CMOS to enhance the quality of digital imaging.
- 20. Imaging drug delivery bio-molecule ultrasensitive sensing thermal cell apoptosis MOREOVER……
- 21. REFERENCES: 1. http://en.wikipedia.org/wiki/Plasmon 2. RAVIPURTI,GUJARAT SAMACHAR NEWS PAPER 15/12/13 3. M. Hoffert et al., Science 298, 981 (2002). http://www.sc.doe.gov/bes/reports/files/SEU_rpt.pdf 4. http://daedalus.caltech.edu/publication/pubs/PlasmonPV_nmat_2010.pdf 5. phy.ntnu.edu.tw/~changmc/Teach/SS/SS_note/chap14.pdf 6. Subsequent Science and Nature articles 1999-2007 7. blogs.ls.berkeley.edu/fengwang/files/2009/12/2006-local-plasmons.pdf 8. www.ncbi.nlm.nih.gov/pubmed/17563412 9. www.amazon.com/Surface-plasmons...application/dp/3838128370 10.en.wikipedia.org/wiki/Plasmonic_solar_cel 11.https://gcep.stanford.edu/pdfs/.../SE_Lee_PlasmonicSolarCells.pdf
- 22. THANK YOU